How to Manually Set and Undervolt your CPU Vcore

Quick way to reduce your temperatures!

A lot of the time when people build their systems, they put it all together, install their OS and programs, and then finish there. However, there are various little tricks you can do to get a little more performance out of your system, as well as reduce the temperatures. In our last guide, we showed you how to manually set your memory frequency, timings and voltage. Now, we show you how to manually set and undervolt your CPU’s Vcore, which should help to reduce your processor’s temperature significantly, and may enable you to run your fans a little slower, leading to an overall quieter system.

Method

First off, you need to download CPU-z here. This shows you what frequencies and voltages your CPU, Memory, and various other components are running at. On the CPU tab, you should be able to see ‘Core Voltage’. The value shown here is the voltage set by Intel to ensure every CPU in that range will run correctly at the stock frequency. The chances are however, that your processor will be able to run at a significantly lower voltage than this, and so by manually undervolting it, your system will remain stable, but operate at a lower temperature.

Now you should download another program called OCCThere. This is a form of stress testing program which puts your CPU through its paces, and simulates a high level of stress to ensure your processor will always be stable. Once downloaded, run the program, select ‘Linpack mode’, then ‘Automatic’. Then choose to run the test for 30 minutes, with an ‘Idle Period’ of zero. Depending on whether your CPU has Hyperthreading or not, you may also need to select ‘Use all Logical Cores’. Then click ‘On’, and let it run for the 30 minutes you set. When the test has finished, on the right hand side of OCCT you’ll be able to see the maximum temperatures your CPU cores reached during the time (and take a note of the figures shown here).

Having done that, you can now restart the computer and enter the BIOS (this is usually done by tapping delete as you press the power button). From here, navigate to the ‘Overclock’ settings. This will probably be under a different name on your motherboard, so you may need to look around in the BIOS to find it. Now you’re on the overclock settings, scroll down the list until you find ‘CPU Core Voltage’, or ‘CPU VCore’. You may need to change a 'mode' setting to manual mode to enable you to change the core voltage.

You should now set the Core voltage to the original value you saw in CPU-z at the start, which in our case was 1.075v. This has now locked the voltage to that value, and so it won’t ever go over that (like it may have done during the initial OCCT test). Now press F10 to save your settings and exit the BIOS, and start up your computer again as normal.

From doing this, you can now run OCCT again (this time for a few hours) to ensure the system is stable, and also you may find temperatures are a little lower. If it is stable (which it should be if you’ve used the initial value you saw in CPU-z), you can now continue to decrease your volts in small increments such as 0.025v until your system is no longer stable. You’ve now found the lowest voltage your system can be stable at.

Finally, back to CPU-z, you can see the core voltage is now at the value you set it to. If you run OCCT again, you should hopefully find that your temperatures are a fair bit lower than they were previously. With our system, we managed to shave off 6 degrees Celsius from our initial test.

Considering the cost of this is merely a bit of time, saving 6 degrees Celsius in temperatures is a significant drop in our eyes. If you're running a stock cooler, or a low end cooler, you may be surprised by how much quieter your system will be, and also how much lower temperatures will be. In our system, we used a Corsair H100i - renowned for being one of the best CPU coolers available. With our 4670k at stock, our H100i won't have been pushed anywhere near the limit. However, with a lower end or stock cooler, where the cooler may be incapable of absorbing the heat generated by the processor, the temperature change between 'Auto' and the lowest voltage could be significantly more than ours.

If you have any questions or problems, feel free to ask over in the OC3D forums.

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